CFD modeling of fish passages (#143)

The practice of fish passage design and construction offers engineers a truly complex, multi-faceted, and hugely diverse set of design considerations that need to be successfully integrated in order to reliably deliver operational success for fish migration, be it across natural or man-built stream obstacles. Among many other considerations remains one central component that is the detailed understanding of the spatially and temporally varying hydraulic conditions throughout the fishway. This includes locations not only within the fishway but also near the approach and exit of the passage in the context of broader scale hydraulics.

While laboratory testing is an important tool for the investigation into the hydraulic characteristics of these structures, Computational Fluid Dynamics (CFD) tools can also offer additional valuable insights. CFD offers extraordinary versatility to assess stream conditions and fishway passage configuration. Using currently available modelling tools, along with available modern computational power, users are able to obtain high accuracy and confidence in the flow solution.

Commercially available CFD tools can now resolve complex free surface flows in their full three dimensional complexity, giving designers a detailed understanding of the velocity field and other key metrics such a turbulent kinetic energy and temperature. In addition, powerful post-processing techniques allow engineers to clearly render regions of high velocity and turbulence.

This presentation will provide examples of CFD models for three common types of passage configurations: a vertical slot structure, a pool and weir with orifice configuration, and a Denil type example. Beyond the CFD modeling aspect, special emphasis will be given to presenting post-processing methods that will allow designers to readily quantify critical flow metrics and fish pathways.